Re: example ligature code.

[David Tooke]

Thanks,

I had previously try ftstrtto.  However, after David suggested it again,  I
re-tried it and realised that I hadn't specified a script of arab, so all
the arab ligatures were not be applied.

Once I entered the right parameters, then it worked great.

I was still having a problem with my program, though.   I was passing the
right parameters but it still wasn't working.

I finally figured out, it was because I applied the Unicode Bidirectional
Algorithm BEFORE calling TT_GSUB_Apply_String.  This re-orders the string
into visual order;  however the ligatures mappings seem to require the
string to be in logical order.

Thanks again for your prompt replies....no doubt I'll be back in touch when
I am trying to figure out how to use GPOS.

David
address@hidden

----- Original Message -----
From: "Werner LEMBERG" <address@hidden>
To: <address@hidden>
Cc: <address@hidden>; <address@hidden>
Sent: Friday, July 21, 2000 12:16 PM
Subject: Re: example ligature code.


>
> > > Does anyone have any example code demonstrating how to use the
> > > GSUB extensions to handle ligatures?  I am rendering some arabic
> > > using the arial font.  The text looks like it should have a
> > > ligature substitution; but none is happening even though I am
> > > using the "liga" feature.
> > >
> > > I know I am doing something wrong, but I would grateful for any
> > > assistance.
> > >
> > I believe that you need to use other features like "fina", etc. for
> > arabic.  Werner and Antoine would probably be able to answer more
> > precisely on this.
>
> As David wrote, please check ftstrtto.  To make ligatures work in
> Arabic it is necessary to activate all tables like this (assuming that
> arab.utf8 contains a small Arabic string in UTF-8 encoding):
>
>   ftstrtto -s arab -f init -f medi -f fina -f liga \
>            -x -u 20 arial.ttf - < arab.utf8
>
> Reason: `liga' is the last OpenType feature applied (the first is
> `init', then `medi' and `fina') and works only after the three other
> tables have adjusted the glyph indices since ligatures depend on the
> position within the Arabic word (e.g. whether it is final or initial).
>
> ftstrtto uses the file arabic.c which assigns Arabic script properties
> to the input characters, according to the algorithm given in the
> Unicode book.
>
> Attached is a sample input file and an image showing the result using
> arial.ttf (version 2.76).
>
>
>     Werner
>